export function registerGLTFLoader(THREE) {

    /**
   * @author Rich Tibbett / https://github.com/richtr
   * @author mrdoob / http://mrdoob.com/
   * @author Tony Parisi / http://www.tonyparisi.com/
   * @author Takahiro / https://github.com/takahirox
   * @author Don McCurdy / https://www.donmccurdy.com
   */

    THREE.GLTFLoader = (function () {

        function GLTFLoader(manager) {

            this.manager = (manager !== undefined) ? manager : THREE.DefaultLoadingManager;
            this.dracoLoader = null;
            this.ddsLoader = null;

        }

        GLTFLoader.prototype = {

            constructor: GLTFLoader,

            crossOrigin: 'anonymous',

            load: function (url, onLoad, onProgress, onError) {

                var scope = this;

                var resourcePath;

                if (this.resourcePath !== undefined) {

                    resourcePath = this.resourcePath;

                } else if (this.path !== undefined) {

                    resourcePath = this.path;

                } else {

                    resourcePath = THREE.LoaderUtils.extractUrlBase(url);

                }

                // Tells the LoadingManager to track an extra item, which resolves after
                // the model is fully loaded. This means the count of items loaded will
                // be incorrect, but ensures manager.onLoad() does not fire early.
                scope.manager.itemStart(url);

                var _onError = function (e) {

                    if (onError) {

                        onError(e);

                    } else {

                        console.error(e);

                    }

                    scope.manager.itemError(url);
                    scope.manager.itemEnd(url);

                };

                var loader = new THREE.FileLoader(scope.manager);

                loader.setPath(this.path);
                loader.setResponseType('arraybuffer');

                if (scope.crossOrigin === 'use-credentials') {

                    loader.setWithCredentials(true);

                }

                loader.load(url, function (data) {

                    try {

                        scope.parse(data, resourcePath, function (gltf) {

                            onLoad(gltf);

                            scope.manager.itemEnd(url);

                        }, _onError);

                    } catch (e) {

                        _onError(e);

                    }

                }, onProgress, _onError);

            },

            setCrossOrigin: function (value) {

                this.crossOrigin = value;
                return this;

            },

            setPath: function (value) {

                this.path = value;
                return this;

            },

            setResourcePath: function (value) {

                this.resourcePath = value;
                return this;

            },

            setDRACOLoader: function (dracoLoader) {

                this.dracoLoader = dracoLoader;
                return this;

            },

            setDDSLoader: function (ddsLoader) {

                this.ddsLoader = ddsLoader;
                return this;

            },

            parse: function (data, path, onLoad, onError) {

                var content;
                var extensions = {};

                if (typeof data === 'string') {

                    content = data;

                } else {

                    var magic = THREE.LoaderUtils.decodeText(new Uint8Array(data, 0, 4));

                    if (magic === BINARY_EXTENSION_HEADER_MAGIC) {

                        try {

                            extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(data);

                        } catch (error) {

                            if (onError) onError(error);
                            return;

                        }

                        content = extensions[EXTENSIONS.KHR_BINARY_GLTF].content;

                    } else {

                        content = THREE.LoaderUtils.decodeText(new Uint8Array(data));

                    }

                }

                var json = JSON.parse(content);

                if (json.asset === undefined || json.asset.version[0] < 2) {

                    if (onError) onError(new Error('THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported. Use LegacyGLTFLoader instead.'));
                    return;

                }

                if (json.extensionsUsed) {

                    for (var i = 0; i < json.extensionsUsed.length; ++i) {

                        var extensionName = json.extensionsUsed[i];
                        var extensionsRequired = json.extensionsRequired || [];

                        switch (extensionName) {

                            case EXTENSIONS.KHR_LIGHTS_PUNCTUAL:
                                extensions[extensionName] = new GLTFLightsExtension(json);
                                break;

                            case EXTENSIONS.KHR_MATERIALS_UNLIT:
                                extensions[extensionName] = new GLTFMaterialsUnlitExtension();
                                break;

                            case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
                                extensions[extensionName] = new GLTFMaterialsPbrSpecularGlossinessExtension();
                                break;

                            case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
                                extensions[extensionName] = new GLTFDracoMeshCompressionExtension(json, this.dracoLoader);
                                break;

                            case EXTENSIONS.MSFT_TEXTURE_DDS:
                                extensions[EXTENSIONS.MSFT_TEXTURE_DDS] = new GLTFTextureDDSExtension(this.ddsLoader);
                                break;

                            case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
                                extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] = new GLTFTextureTransformExtension();
                                break;

                            default:

                                if (extensionsRequired.indexOf(extensionName) >= 0) {

                                    console.warn('THREE.GLTFLoader: Unknown extension "' + extensionName + '".');

                                }

                        }

                    }

                }

                var parser = new GLTFParser(json, extensions, {

                    path: path || this.resourcePath || '',
                    crossOrigin: this.crossOrigin,
                    manager: this.manager

                });

                parser.parse(onLoad, onError);

            }

        };

        /* GLTFREGISTRY */

        function GLTFRegistry() {

            var objects = {};

            return {

                get: function (key) {

                    return objects[key];

                },

                add: function (key, object) {

                    objects[key] = object;

                },

                remove: function (key) {

                    delete objects[key];

                },

                removeAll: function () {

                    objects = {};

                }

            };

        }

        /*********************************/
        /********** EXTENSIONS ***********/
        /*********************************/

        var EXTENSIONS = {
            KHR_BINARY_GLTF: 'KHR_binary_glTF',
            KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
            KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
            KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
            KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
            KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
            MSFT_TEXTURE_DDS: 'MSFT_texture_dds'
        };

        /**
         * DDS Texture Extension
         *
         * Specification:
         * https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
         *
         */
        function GLTFTextureDDSExtension(ddsLoader) {

            if (!ddsLoader) {

                throw new Error('THREE.GLTFLoader: Attempting to load .dds texture without importing THREE.DDSLoader');

            }

            this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
            this.ddsLoader = ddsLoader;

        }

        /**
         * Lights Extension
         *
         * Specification: PENDING
         */
        function GLTFLightsExtension(json) {

            this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

            var extension = (json.extensions && json.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]) || {};
            this.lightDefs = extension.lights || [];

        }

        GLTFLightsExtension.prototype.loadLight = function (lightIndex) {

            var lightDef = this.lightDefs[lightIndex];
            var lightNode;

            var color = new THREE.Color(0xffffff);
            if (lightDef.color !== undefined) color.fromArray(lightDef.color);

            var range = lightDef.range !== undefined ? lightDef.range : 0;

            switch (lightDef.type) {

                case 'directional':
                    lightNode = new THREE.DirectionalLight(color);
                    lightNode.target.position.set(0, 0, - 1);
                    lightNode.add(lightNode.target);
                    break;

                case 'point':
                    lightNode = new THREE.PointLight(color);
                    lightNode.distance = range;
                    break;

                case 'spot':
                    lightNode = new THREE.SpotLight(color);
                    lightNode.distance = range;
                    // Handle spotlight properties.
                    lightDef.spot = lightDef.spot || {};
                    lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
                    lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
                    lightNode.angle = lightDef.spot.outerConeAngle;
                    lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
                    lightNode.target.position.set(0, 0, - 1);
                    lightNode.add(lightNode.target);
                    break;

                default:
                    throw new Error('THREE.GLTFLoader: Unexpected light type, "' + lightDef.type + '".');

            }

            // Some lights (e.g. spot) default to a position other than the origin. Reset the position
            // here, because node-level parsing will only override position if explicitly specified.
            lightNode.position.set(0, 0, 0);

            lightNode.decay = 2;

            if (lightDef.intensity !== undefined) lightNode.intensity = lightDef.intensity;

            lightNode.name = lightDef.name || ('light_' + lightIndex);

            return Promise.resolve(lightNode);

        };

        /**
         * Unlit Materials Extension (pending)
         *
         * PR: https://github.com/KhronosGroup/glTF/pull/1163
         */
        function GLTFMaterialsUnlitExtension() {

            this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;

        }

        GLTFMaterialsUnlitExtension.prototype.getMaterialType = function () {

            return THREE.MeshBasicMaterial;

        };

        GLTFMaterialsUnlitExtension.prototype.extendParams = function (materialParams, materialDef, parser) {

            var pending = [];

            materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
            materialParams.opacity = 1.0;

            var metallicRoughness = materialDef.pbrMetallicRoughness;

            if (metallicRoughness) {

                if (Array.isArray(metallicRoughness.baseColorFactor)) {

                    var array = metallicRoughness.baseColorFactor;

                    materialParams.color.fromArray(array);
                    materialParams.opacity = array[3];

                }

                if (metallicRoughness.baseColorTexture !== undefined) {

                    pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));

                }

            }

            return Promise.all(pending);

        };

        /* BINARY EXTENSION */
        var BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
        var BINARY_EXTENSION_HEADER_LENGTH = 12;
        var BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };

        function GLTFBinaryExtension(data) {

            this.name = EXTENSIONS.KHR_BINARY_GLTF;
            this.content = null;
            this.body = null;

            var headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH);

            this.header = {
                magic: THREE.LoaderUtils.decodeText(new Uint8Array(data.slice(0, 4))),
                version: headerView.getUint32(4, true),
                length: headerView.getUint32(8, true)
            };

            if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {

                throw new Error('THREE.GLTFLoader: Unsupported glTF-Binary header.');

            } else if (this.header.version < 2.0) {

                throw new Error('THREE.GLTFLoader: Legacy binary file detected. Use LegacyGLTFLoader instead.');

            }

            var chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH);
            var chunkIndex = 0;

            while (chunkIndex < chunkView.byteLength) {

                var chunkLength = chunkView.getUint32(chunkIndex, true);
                chunkIndex += 4;

                var chunkType = chunkView.getUint32(chunkIndex, true);
                chunkIndex += 4;

                if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {

                    var contentArray = new Uint8Array(data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength);
                    this.content = THREE.LoaderUtils.decodeText(contentArray);

                } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {

                    var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
                    this.body = data.slice(byteOffset, byteOffset + chunkLength);

                }

                // Clients must ignore chunks with unknown types.

                chunkIndex += chunkLength;

            }

            if (this.content === null) {

                throw new Error('THREE.GLTFLoader: JSON content not found.');

            }

        }

        /**
         * DRACO Mesh Compression Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/pull/874
         */
        function GLTFDracoMeshCompressionExtension(json, dracoLoader) {

            if (!dracoLoader) {

                throw new Error('THREE.GLTFLoader: No DRACOLoader instance provided.');

            }

            this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
            this.json = json;
            this.dracoLoader = dracoLoader;

        }

        GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function (primitive, parser) {

            var json = this.json;
            var dracoLoader = this.dracoLoader;
            var bufferViewIndex = primitive.extensions[this.name].bufferView;
            var gltfAttributeMap = primitive.extensions[this.name].attributes;
            var threeAttributeMap = {};
            var attributeNormalizedMap = {};
            var attributeTypeMap = {};

            for (var attributeName in gltfAttributeMap) {

                var threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();

                threeAttributeMap[threeAttributeName] = gltfAttributeMap[attributeName];

            }

            for (attributeName in primitive.attributes) {

                var threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();

                if (gltfAttributeMap[attributeName] !== undefined) {

                    var accessorDef = json.accessors[primitive.attributes[attributeName]];
                    var componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

                    attributeTypeMap[threeAttributeName] = componentType;
                    attributeNormalizedMap[threeAttributeName] = accessorDef.normalized === true;

                }

            }

            return parser.getDependency('bufferView', bufferViewIndex).then(function (bufferView) {

                return new Promise(function (resolve) {

                    dracoLoader.decodeDracoFile(bufferView, function (geometry) {

                        for (var attributeName in geometry.attributes) {

                            var attribute = geometry.attributes[attributeName];
                            var normalized = attributeNormalizedMap[attributeName];

                            if (normalized !== undefined) attribute.normalized = normalized;

                        }

                        resolve(geometry);

                    }, threeAttributeMap, attributeTypeMap);

                });

            });

        };

        /**
         * Texture Transform Extension
         *
         * Specification:
         */
        function GLTFTextureTransformExtension() {

            this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;

        }

        GLTFTextureTransformExtension.prototype.extendTexture = function (texture, transform) {

            texture = texture.clone();

            if (transform.offset !== undefined) {

                texture.offset.fromArray(transform.offset);

            }

            if (transform.rotation !== undefined) {

                texture.rotation = transform.rotation;

            }

            if (transform.scale !== undefined) {

                texture.repeat.fromArray(transform.scale);

            }

            if (transform.texCoord !== undefined) {

                console.warn('THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.');

            }

            texture.needsUpdate = true;

            return texture;

        };

        /**
         * Specular-Glossiness Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
         */
        function GLTFMaterialsPbrSpecularGlossinessExtension() {

            return {

                name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,

                specularGlossinessParams: [
                    'color',
                    'map',
                    'lightMap',
                    'lightMapIntensity',
                    'aoMap',
                    'aoMapIntensity',
                    'emissive',
                    'emissiveIntensity',
                    'emissiveMap',
                    'bumpMap',
                    'bumpScale',
                    'normalMap',
                    'displacementMap',
                    'displacementScale',
                    'displacementBias',
                    'specularMap',
                    'specular',
                    'glossinessMap',
                    'glossiness',
                    'alphaMap',
                    'envMap',
                    'envMapIntensity',
                    'refractionRatio',
                ],

                getMaterialType: function () {

                    return THREE.ShaderMaterial;

                },

                extendParams: function (materialParams, materialDef, parser) {

                    var pbrSpecularGlossiness = materialDef.extensions[this.name];

                    var shader = THREE.ShaderLib['standard'];

                    var uniforms = THREE.UniformsUtils.clone(shader.uniforms);

                    var specularMapParsFragmentChunk = [
                        '#ifdef USE_SPECULARMAP',
                        '	uniform sampler2D specularMap;',
                        '#endif'
                    ].join('\n');

                    var glossinessMapParsFragmentChunk = [
                        '#ifdef USE_GLOSSINESSMAP',
                        '	uniform sampler2D glossinessMap;',
                        '#endif'
                    ].join('\n');

                    var specularMapFragmentChunk = [
                        'vec3 specularFactor = specular;',
                        '#ifdef USE_SPECULARMAP',
                        '	vec4 texelSpecular = texture2D( specularMap, vUv );',
                        '	texelSpecular = sRGBToLinear( texelSpecular );',
                        '	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
                        '	specularFactor *= texelSpecular.rgb;',
                        '#endif'
                    ].join('\n');

                    var glossinessMapFragmentChunk = [
                        'float glossinessFactor = glossiness;',
                        '#ifdef USE_GLOSSINESSMAP',
                        '	vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
                        '	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
                        '	glossinessFactor *= texelGlossiness.a;',
                        '#endif'
                    ].join('\n');

                    var lightPhysicalFragmentChunk = [
                        'PhysicalMaterial material;',
                        'material.diffuseColor = diffuseColor.rgb;',
                        'material.specularRoughness = clamp( 1.0 - glossinessFactor, 0.04, 1.0 );',
                        'material.specularColor = specularFactor.rgb;',
                    ].join('\n');

                    var fragmentShader = shader.fragmentShader
                        .replace('uniform float roughness;', 'uniform vec3 specular;')
                        .replace('uniform float metalness;', 'uniform float glossiness;')
                        .replace('#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk)
                        .replace('#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk)
                        .replace('#include <roughnessmap_fragment>', specularMapFragmentChunk)
                        .replace('#include <metalnessmap_fragment>', glossinessMapFragmentChunk)
                        .replace('#include <lights_physical_fragment>', lightPhysicalFragmentChunk);

                    delete uniforms.roughness;
                    delete uniforms.metalness;
                    delete uniforms.roughnessMap;
                    delete uniforms.metalnessMap;

                    uniforms.specular = { value: new THREE.Color().setHex(0x111111) };
                    uniforms.glossiness = { value: 0.5 };
                    uniforms.specularMap = { value: null };
                    uniforms.glossinessMap = { value: null };

                    materialParams.vertexShader = shader.vertexShader;
                    materialParams.fragmentShader = fragmentShader;
                    materialParams.uniforms = uniforms;
                    materialParams.defines = { 'STANDARD': '' }

                    materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
                    materialParams.opacity = 1.0;

                    var pending = [];

                    if (Array.isArray(pbrSpecularGlossiness.diffuseFactor)) {

                        var array = pbrSpecularGlossiness.diffuseFactor;

                        materialParams.color.fromArray(array);
                        materialParams.opacity = array[3];

                    }

                    if (pbrSpecularGlossiness.diffuseTexture !== undefined) {

                        pending.push(parser.assignTexture(materialParams, 'map', pbrSpecularGlossiness.diffuseTexture));

                    }

                    materialParams.emissive = new THREE.Color(0.0, 0.0, 0.0);
                    materialParams.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
                    materialParams.specular = new THREE.Color(1.0, 1.0, 1.0);

                    if (Array.isArray(pbrSpecularGlossiness.specularFactor)) {

                        materialParams.specular.fromArray(pbrSpecularGlossiness.specularFactor);

                    }

                    if (pbrSpecularGlossiness.specularGlossinessTexture !== undefined) {

                        var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
                        pending.push(parser.assignTexture(materialParams, 'glossinessMap', specGlossMapDef));
                        pending.push(parser.assignTexture(materialParams, 'specularMap', specGlossMapDef));

                    }

                    return Promise.all(pending);

                },

                createMaterial: function (params) {

                    // setup material properties based on MeshStandardMaterial for Specular-Glossiness

                    var material = new THREE.ShaderMaterial({
                        defines: params.defines,
                        vertexShader: params.vertexShader,
                        fragmentShader: params.fragmentShader,
                        uniforms: params.uniforms,
                        fog: true,
                        lights: true,
                        opacity: params.opacity,
                        transparent: params.transparent
                    });

                    material.isGLTFSpecularGlossinessMaterial = true;

                    material.color = params.color;

                    material.map = params.map === undefined ? null : params.map;

                    material.lightMap = null;
                    material.lightMapIntensity = 1.0;

                    material.aoMap = params.aoMap === undefined ? null : params.aoMap;
                    material.aoMapIntensity = 1.0;

                    material.emissive = params.emissive;
                    material.emissiveIntensity = 1.0;
                    material.emissiveMap = params.emissiveMap === undefined ? null : params.emissiveMap;

                    material.bumpMap = params.bumpMap === undefined ? null : params.bumpMap;
                    material.bumpScale = 1;

                    material.normalMap = params.normalMap === undefined ? null : params.normalMap;

                    if (params.normalScale) material.normalScale = params.normalScale;

                    material.displacementMap = null;
                    material.displacementScale = 1;
                    material.displacementBias = 0;

                    material.specularMap = params.specularMap === undefined ? null : params.specularMap;
                    material.specular = params.specular;

                    material.glossinessMap = params.glossinessMap === undefined ? null : params.glossinessMap;
                    material.glossiness = params.glossiness;

                    material.alphaMap = null;

                    material.envMap = params.envMap === undefined ? null : params.envMap;
                    material.envMapIntensity = 1.0;

                    material.refractionRatio = 0.98;

                    material.extensions.derivatives = true;

                    return material;

                },

                /**
                 * Clones a GLTFSpecularGlossinessMaterial instance. The ShaderMaterial.copy() method can
                 * copy only properties it knows about or inherits, and misses many properties that would
                 * normally be defined by MeshStandardMaterial.
                 *
                 * This method allows GLTFSpecularGlossinessMaterials to be cloned in the process of
                 * loading a glTF model, but cloning later (e.g. by the user) would require these changes
                 * AND also updating `.onBeforeRender` on the parent mesh.
                 *
                 * @param  {THREE.ShaderMaterial} source
                 * @return {THREE.ShaderMaterial}
                 */
                cloneMaterial: function (source) {

                    var target = source.clone();

                    target.isGLTFSpecularGlossinessMaterial = true;

                    var params = this.specularGlossinessParams;

                    for (var i = 0, il = params.length; i < il; i++) {

                        var value = source[params[i]];
                        target[params[i]] = (value && value.isColor) ? value.clone() : value;

                    }

                    return target;

                },

                // Here's based on refreshUniformsCommon() and refreshUniformsStandard() in WebGLRenderer.
                refreshUniforms: function (renderer, scene, camera, geometry, material) {

                    if (material.isGLTFSpecularGlossinessMaterial !== true) {

                        return;

                    }

                    var uniforms = material.uniforms;
                    var defines = material.defines;

                    uniforms.opacity.value = material.opacity;

                    uniforms.diffuse.value.copy(material.color);
                    uniforms.emissive.value.copy(material.emissive).multiplyScalar(material.emissiveIntensity);

                    uniforms.map.value = material.map;
                    uniforms.specularMap.value = material.specularMap;
                    uniforms.alphaMap.value = material.alphaMap;

                    uniforms.lightMap.value = material.lightMap;
                    uniforms.lightMapIntensity.value = material.lightMapIntensity;

                    uniforms.aoMap.value = material.aoMap;
                    uniforms.aoMapIntensity.value = material.aoMapIntensity;

                    // uv repeat and offset setting priorities
                    // 1. color map
                    // 2. specular map
                    // 3. normal map
                    // 4. bump map
                    // 5. alpha map
                    // 6. emissive map

                    var uvScaleMap;

                    if (material.map) {

                        uvScaleMap = material.map;

                    } else if (material.specularMap) {

                        uvScaleMap = material.specularMap;

                    } else if (material.displacementMap) {

                        uvScaleMap = material.displacementMap;

                    } else if (material.normalMap) {

                        uvScaleMap = material.normalMap;

                    } else if (material.bumpMap) {

                        uvScaleMap = material.bumpMap;

                    } else if (material.glossinessMap) {

                        uvScaleMap = material.glossinessMap;

                    } else if (material.alphaMap) {

                        uvScaleMap = material.alphaMap;

                    } else if (material.emissiveMap) {

                        uvScaleMap = material.emissiveMap;

                    }

                    if (uvScaleMap !== undefined) {

                        // backwards compatibility
                        if (uvScaleMap.isWebGLRenderTarget) {

                            uvScaleMap = uvScaleMap.texture;

                        }

                        if (uvScaleMap.matrixAutoUpdate === true) {

                            uvScaleMap.updateMatrix();

                        }

                        uniforms.uvTransform.value.copy(uvScaleMap.matrix);

                    }

                    if (material.envMap) {

                        uniforms.envMap.value = material.envMap;
                        uniforms.envMapIntensity.value = material.envMapIntensity;

                        // don't flip CubeTexture envMaps, flip everything else:
                        //  WebGLRenderTargetCube will be flipped for backwards compatibility
                        //  WebGLRenderTargetCube.texture will be flipped because it's a Texture and NOT a CubeTexture
                        // this check must be handled differently, or removed entirely, if WebGLRenderTargetCube uses a CubeTexture in the future
                        uniforms.flipEnvMap.value = material.envMap.isCubeTexture ? - 1 : 1;

                        uniforms.reflectivity.value = material.reflectivity;
                        uniforms.refractionRatio.value = material.refractionRatio;

                        uniforms.maxMipLevel.value = renderer.properties.get(material.envMap).__maxMipLevel;

                    }

                    uniforms.specular.value.copy(material.specular);
                    uniforms.glossiness.value = material.glossiness;

                    uniforms.glossinessMap.value = material.glossinessMap;

                    uniforms.emissiveMap.value = material.emissiveMap;
                    uniforms.bumpMap.value = material.bumpMap;
                    uniforms.normalMap.value = material.normalMap;

                    uniforms.displacementMap.value = material.displacementMap;
                    uniforms.displacementScale.value = material.displacementScale;
                    uniforms.displacementBias.value = material.displacementBias;

                    if (uniforms.glossinessMap.value !== null && defines.USE_GLOSSINESSMAP === undefined) {

                        defines.USE_GLOSSINESSMAP = '';
                        // set USE_ROUGHNESSMAP to enable vUv
                        defines.USE_ROUGHNESSMAP = '';

                    }

                    if (uniforms.glossinessMap.value === null && defines.USE_GLOSSINESSMAP !== undefined) {

                        delete defines.USE_GLOSSINESSMAP;
                        delete defines.USE_ROUGHNESSMAP;

                    }

                }

            };

        }

        /*********************************/
        /********** INTERPOLATION ********/
        /*********************************/

        // Spline Interpolation
        // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
        function GLTFCubicSplineInterpolant(parameterPositions, sampleValues, sampleSize, resultBuffer) {

            THREE.Interpolant.call(this, parameterPositions, sampleValues, sampleSize, resultBuffer);

        }

        GLTFCubicSplineInterpolant.prototype = Object.create(THREE.Interpolant.prototype);
        GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;

        GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function (index) {

            // Copies a sample value to the result buffer. See description of glTF
            // CUBICSPLINE values layout in interpolate_() function below.

            var result = this.resultBuffer,
                values = this.sampleValues,
                valueSize = this.valueSize,
                offset = index * valueSize * 3 + valueSize;

            for (var i = 0; i !== valueSize; i++) {

                result[i] = values[offset + i];

            }

            return result;

        };

        GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

        GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

        GLTFCubicSplineInterpolant.prototype.interpolate_ = function (i1, t0, t, t1) {

            var result = this.resultBuffer;
            var values = this.sampleValues;
            var stride = this.valueSize;

            var stride2 = stride * 2;
            var stride3 = stride * 3;

            var td = t1 - t0;

            var p = (t - t0) / td;
            var pp = p * p;
            var ppp = pp * p;

            var offset1 = i1 * stride3;
            var offset0 = offset1 - stride3;

            var s2 = - 2 * ppp + 3 * pp;
            var s3 = ppp - pp;
            var s0 = 1 - s2;
            var s1 = s3 - pp + p;

            // Layout of keyframe output values for CUBICSPLINE animations:
            //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
            for (var i = 0; i !== stride; i++) {

                var p0 = values[offset0 + i + stride]; // splineVertex_k
                var m0 = values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
                var p1 = values[offset1 + i + stride]; // splineVertex_k+1
                var m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)

                result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;

            }

            return result;

        };

        /*********************************/
        /********** INTERNALS ************/
        /*********************************/

        /* CONSTANTS */

        var WEBGL_CONSTANTS = {
            FLOAT: 5126,
            //FLOAT_MAT2: 35674,
            FLOAT_MAT3: 35675,
            FLOAT_MAT4: 35676,
            FLOAT_VEC2: 35664,
            FLOAT_VEC3: 35665,
            FLOAT_VEC4: 35666,
            LINEAR: 9729,
            REPEAT: 10497,
            SAMPLER_2D: 35678,
            POINTS: 0,
            LINES: 1,
            LINE_LOOP: 2,
            LINE_STRIP: 3,
            TRIANGLES: 4,
            TRIANGLE_STRIP: 5,
            TRIANGLE_FAN: 6,
            UNSIGNED_BYTE: 5121,
            UNSIGNED_SHORT: 5123
        };

        var WEBGL_COMPONENT_TYPES = {
            5120: Int8Array,
            5121: Uint8Array,
            5122: Int16Array,
            5123: Uint16Array,
            5125: Uint32Array,
            5126: Float32Array
        };

        var WEBGL_FILTERS = {
            9728: THREE.NearestFilter,
            9729: THREE.LinearFilter,
            9984: THREE.NearestMipmapNearestFilter,
            9985: THREE.LinearMipmapNearestFilter,
            9986: THREE.NearestMipmapLinearFilter,
            9987: THREE.LinearMipmapLinearFilter
        };

        var WEBGL_WRAPPINGS = {
            33071: THREE.ClampToEdgeWrapping,
            33648: THREE.MirroredRepeatWrapping,
            10497: THREE.RepeatWrapping
        };

        var WEBGL_TYPE_SIZES = {
            'SCALAR': 1,
            'VEC2': 2,
            'VEC3': 3,
            'VEC4': 4,
            'MAT2': 4,
            'MAT3': 9,
            'MAT4': 16
        };

        var ATTRIBUTES = {
            POSITION: 'position',
            NORMAL: 'normal',
            TANGENT: 'tangent',
            TEXCOORD_0: 'uv',
            TEXCOORD_1: 'uv2',
            COLOR_0: 'color',
            WEIGHTS_0: 'skinWeight',
            JOINTS_0: 'skinIndex',
        };

        var PATH_PROPERTIES = {
            scale: 'scale',
            translation: 'position',
            rotation: 'quaternion',
            weights: 'morphTargetInfluences'
        };

        var INTERPOLATION = {
            CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
            // keyframe track will be initialized with a default interpolation type, then modified.
            LINEAR: THREE.InterpolateLinear,
            STEP: THREE.InterpolateDiscrete
        };

        var ALPHA_MODES = {
            OPAQUE: 'OPAQUE',
            MASK: 'MASK',
            BLEND: 'BLEND'
        };

        var MIME_TYPE_FORMATS = {
            'image/png': THREE.RGBAFormat,
            'image/jpeg': THREE.RGBFormat
        };

        /* UTILITY FUNCTIONS */

        function resolveURL(url, path) {

            // Invalid URL
            if (typeof url !== 'string' || url === '') return '';

            // Host Relative URL
            if (/^https?:\/\//i.test(path) && /^\//.test(url)) {

                path = path.replace(/(^https?:\/\/[^\/]+).*/i, '$1');

            }

            // Absolute URL http://,https://,//
            if (/^(https?:)?\/\//i.test(url)) return url;

            // Data URI
            if (/^data:.*,.*$/i.test(url)) return url;

            // Blob URL
            if (/^blob:.*$/i.test(url)) return url;

            // Relative URL
            return path + url;

        }

        var defaultMaterial;

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
         */
        function createDefaultMaterial() {

            defaultMaterial = defaultMaterial || new THREE.MeshStandardMaterial({
                color: 0xFFFFFF,
                emissive: 0x000000,
                metalness: 1,
                roughness: 1,
                transparent: false,
                depthTest: true,
                side: THREE.FrontSide
            });

            return defaultMaterial;

        }

        function addUnknownExtensionsToUserData(knownExtensions, object, objectDef) {

            // Add unknown glTF extensions to an object's userData.

            for (var name in objectDef.extensions) {

                if (knownExtensions[name] === undefined) {

                    object.userData.gltfExtensions = object.userData.gltfExtensions || {};
                    object.userData.gltfExtensions[name] = objectDef.extensions[name];

                }

            }

        }

        /**
         * @param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
         * @param {GLTF.definition} gltfDef
         */
        function assignExtrasToUserData(object, gltfDef) {

            if (gltfDef.extras !== undefined) {

                if (typeof gltfDef.extras === 'object') {

                    Object.assign(object.userData, gltfDef.extras);

                } else {

                    console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras);

                }

            }

        }

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
         *
         * @param {THREE.BufferGeometry} geometry
         * @param {Array<GLTF.Target>} targets
         * @param {GLTFParser} parser
         * @return {Promise<THREE.BufferGeometry>}
         */
        function addMorphTargets(geometry, targets, parser) {

            var hasMorphPosition = false;
            var hasMorphNormal = false;

            for (var i = 0, il = targets.length; i < il; i++) {

                var target = targets[i];

                if (target.POSITION !== undefined) hasMorphPosition = true;
                if (target.NORMAL !== undefined) hasMorphNormal = true;

                if (hasMorphPosition && hasMorphNormal) break;

            }

            if (!hasMorphPosition && !hasMorphNormal) return Promise.resolve(geometry);

            var pendingPositionAccessors = [];
            var pendingNormalAccessors = [];

            for (var i = 0, il = targets.length; i < il; i++) {

                var target = targets[i];

                if (hasMorphPosition) {

                    var pendingAccessor = target.POSITION !== undefined
                        ? parser.getDependency('accessor', target.POSITION)
                        : geometry.attributes.position;

                    pendingPositionAccessors.push(pendingAccessor);

                }

                if (hasMorphNormal) {

                    var pendingAccessor = target.NORMAL !== undefined
                        ? parser.getDependency('accessor', target.NORMAL)
                        : geometry.attributes.normal;

                    pendingNormalAccessors.push(pendingAccessor);

                }

            }

            return Promise.all([
                Promise.all(pendingPositionAccessors),
                Promise.all(pendingNormalAccessors)
            ]).then(function (accessors) {

                var morphPositions = accessors[0];
                var morphNormals = accessors[1];

                // Clone morph target accessors before modifying them.

                for (var i = 0, il = morphPositions.length; i < il; i++) {

                    if (geometry.attributes.position === morphPositions[i]) continue;

                    morphPositions[i] = cloneBufferAttribute(morphPositions[i]);

                }

                for (var i = 0, il = morphNormals.length; i < il; i++) {

                    if (geometry.attributes.normal === morphNormals[i]) continue;

                    morphNormals[i] = cloneBufferAttribute(morphNormals[i]);

                }

                for (var i = 0, il = targets.length; i < il; i++) {

                    var target = targets[i];
                    var attributeName = 'morphTarget' + i;

                    if (hasMorphPosition) {

                        // Three.js morph position is absolute value. The formula is
                        //   basePosition
                        //     + weight0 * ( morphPosition0 - basePosition )
                        //     + weight1 * ( morphPosition1 - basePosition )
                        //     ...
                        // while the glTF one is relative
                        //   basePosition
                        //     + weight0 * glTFmorphPosition0
                        //     + weight1 * glTFmorphPosition1
                        //     ...
                        // then we need to convert from relative to absolute here.

                        if (target.POSITION !== undefined) {

                            var positionAttribute = morphPositions[i];
                            positionAttribute.name = attributeName;

                            var position = geometry.attributes.position;

                            for (var j = 0, jl = positionAttribute.count; j < jl; j++) {

                                positionAttribute.setXYZ(
                                    j,
                                    positionAttribute.getX(j) + position.getX(j),
                                    positionAttribute.getY(j) + position.getY(j),
                                    positionAttribute.getZ(j) + position.getZ(j)
                                );

                            }

                        }

                    }

                    if (hasMorphNormal) {

                        // see target.POSITION's comment

                        if (target.NORMAL !== undefined) {

                            var normalAttribute = morphNormals[i];
                            normalAttribute.name = attributeName;

                            var normal = geometry.attributes.normal;

                            for (var j = 0, jl = normalAttribute.count; j < jl; j++) {

                                normalAttribute.setXYZ(
                                    j,
                                    normalAttribute.getX(j) + normal.getX(j),
                                    normalAttribute.getY(j) + normal.getY(j),
                                    normalAttribute.getZ(j) + normal.getZ(j)
                                );

                            }

                        }

                    }

                }

                if (hasMorphPosition) geometry.morphAttributes.position = morphPositions;
                if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals;

                return geometry;

            });

        }

        /**
         * @param {THREE.Mesh} mesh
         * @param {GLTF.Mesh} meshDef
         */
        function updateMorphTargets(mesh, meshDef) {

            mesh.updateMorphTargets();

            if (meshDef.weights !== undefined) {

                for (var i = 0, il = meshDef.weights.length; i < il; i++) {

                    mesh.morphTargetInfluences[i] = meshDef.weights[i];

                }

            }

            // .extras has user-defined data, so check that .extras.targetNames is an array.
            if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {

                var targetNames = meshDef.extras.targetNames;

                if (mesh.morphTargetInfluences.length === targetNames.length) {

                    mesh.morphTargetDictionary = {};

                    for (var i = 0, il = targetNames.length; i < il; i++) {

                        mesh.morphTargetDictionary[targetNames[i]] = i;

                    }

                } else {

                    console.warn('THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.');

                }

            }

        }

        function createPrimitiveKey(primitiveDef) {

            var dracoExtension = primitiveDef.extensions && primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION];
            var geometryKey;

            if (dracoExtension) {

                geometryKey = 'draco:' + dracoExtension.bufferView
                    + ':' + dracoExtension.indices
                    + ':' + createAttributesKey(dracoExtension.attributes);

            } else {

                geometryKey = primitiveDef.indices + ':' + createAttributesKey(primitiveDef.attributes) + ':' + primitiveDef.mode;

            }

            return geometryKey;

        }

        function createAttributesKey(attributes) {

            var attributesKey = '';

            var keys = Object.keys(attributes).sort();

            for (var i = 0, il = keys.length; i < il; i++) {

                attributesKey += keys[i] + ':' + attributes[keys[i]] + ';';

            }

            return attributesKey;

        }

        function cloneBufferAttribute(attribute) {

            if (attribute.isInterleavedBufferAttribute) {

                var count = attribute.count;
                var itemSize = attribute.itemSize;
                var array = attribute.array.slice(0, count * itemSize);

                for (var i = 0, j = 0; i < count; ++i) {

                    array[j++] = attribute.getX(i);
                    if (itemSize >= 2) array[j++] = attribute.getY(i);
                    if (itemSize >= 3) array[j++] = attribute.getZ(i);
                    if (itemSize >= 4) array[j++] = attribute.getW(i);

                }

                return new THREE.BufferAttribute(array, itemSize, attribute.normalized);

            }

            return attribute.clone();

        }

        /* GLTF PARSER */

        function GLTFParser(json, extensions, options) {

            this.json = json || {};
            this.extensions = extensions || {};
            this.options = options || {};

            // loader object cache
            this.cache = new GLTFRegistry();

            // BufferGeometry caching
            this.primitiveCache = {};

            this.textureLoader = new THREE.TextureLoader(this.options.manager);
            this.textureLoader.setCrossOrigin(this.options.crossOrigin);

            this.fileLoader = new THREE.FileLoader(this.options.manager);
            this.fileLoader.setResponseType('arraybuffer');

            if (this.options.crossOrigin === 'use-credentials') {

                this.fileLoader.setWithCredentials(true);

            }

        }

        GLTFParser.prototype.parse = function (onLoad, onError) {

            var parser = this;
            var json = this.json;
            var extensions = this.extensions;

            // Clear the loader cache
            this.cache.removeAll();

            // Mark the special nodes/meshes in json for efficient parse
            this.markDefs();

            Promise.all([

                this.getDependencies('scene'),
                this.getDependencies('animation'),
                this.getDependencies('camera'),

            ]).then(function (dependencies) {

                var result = {
                    scene: dependencies[0][json.scene || 0],
                    scenes: dependencies[0],
                    animations: dependencies[1],
                    cameras: dependencies[2],
                    asset: json.asset,
                    parser: parser,
                    userData: {}
                };

                addUnknownExtensionsToUserData(extensions, result, json);

                assignExtrasToUserData(result, json);

                onLoad(result);

            }).catch(onError);

        };

        /**
         * Marks the special nodes/meshes in json for efficient parse.
         */
        GLTFParser.prototype.markDefs = function () {

            var nodeDefs = this.json.nodes || [];
            var skinDefs = this.json.skins || [];
            var meshDefs = this.json.meshes || [];

            var meshReferences = {};
            var meshUses = {};

            // Nothing in the node definition indicates whether it is a Bone or an
            // Object3D. Use the skins' joint references to mark bones.
            for (var skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex++) {

                var joints = skinDefs[skinIndex].joints;

                for (var i = 0, il = joints.length; i < il; i++) {

                    nodeDefs[joints[i]].isBone = true;

                }

            }

            // Meshes can (and should) be reused by multiple nodes in a glTF asset. To
            // avoid having more than one THREE.Mesh with the same name, count
            // references and rename instances below.
            //
            // Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
            for (var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {

                var nodeDef = nodeDefs[nodeIndex];

                if (nodeDef.mesh !== undefined) {

                    if (meshReferences[nodeDef.mesh] === undefined) {

                        meshReferences[nodeDef.mesh] = meshUses[nodeDef.mesh] = 0;

                    }

                    meshReferences[nodeDef.mesh]++;

                    // Nothing in the mesh definition indicates whether it is
                    // a SkinnedMesh or Mesh. Use the node's mesh reference
                    // to mark SkinnedMesh if node has skin.
                    if (nodeDef.skin !== undefined) {

                        meshDefs[nodeDef.mesh].isSkinnedMesh = true;

                    }

                }

            }

            this.json.meshReferences = meshReferences;
            this.json.meshUses = meshUses;

        };

        /**
         * Requests the specified dependency asynchronously, with caching.
         * @param {string} type
         * @param {number} index
         * @return {Promise<THREE.Object3D|THREE.Material|THREE.Texture|THREE.AnimationClip|ArrayBuffer|Object>}
         */
        GLTFParser.prototype.getDependency = function (type, index) {

            var cacheKey = type + ':' + index;
            var dependency = this.cache.get(cacheKey);

            if (!dependency) {

                switch (type) {

                    case 'scene':
                        dependency = this.loadScene(index);
                        break;

                    case 'node':
                        dependency = this.loadNode(index);
                        break;

                    case 'mesh':
                        dependency = this.loadMesh(index);
                        break;

                    case 'accessor':
                        dependency = this.loadAccessor(index);
                        break;

                    case 'bufferView':
                        dependency = this.loadBufferView(index);
                        break;

                    case 'buffer':
                        dependency = this.loadBuffer(index);
                        break;

                    case 'material':
                        dependency = this.loadMaterial(index);
                        break;

                    case 'texture':
                        dependency = this.loadTexture(index);
                        break;

                    case 'skin':
                        dependency = this.loadSkin(index);
                        break;

                    case 'animation':
                        dependency = this.loadAnimation(index);
                        break;

                    case 'camera':
                        dependency = this.loadCamera(index);
                        break;

                    case 'light':
                        dependency = this.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].loadLight(index);
                        break;

                    default:
                        throw new Error('Unknown type: ' + type);

                }

                this.cache.add(cacheKey, dependency);

            }

            return dependency;

        };

        /**
         * Requests all dependencies of the specified type asynchronously, with caching.
         * @param {string} type
         * @return {Promise<Array<Object>>}
         */
        GLTFParser.prototype.getDependencies = function (type) {

            var dependencies = this.cache.get(type);

            if (!dependencies) {

                var parser = this;
                var defs = this.json[type + (type === 'mesh' ? 'es' : 's')] || [];

                dependencies = Promise.all(defs.map(function (def, index) {

                    return parser.getDependency(type, index);

                }));

                this.cache.add(type, dependencies);

            }

            return dependencies;

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
         * @param {number} bufferIndex
         * @return {Promise<ArrayBuffer>}
         */
        GLTFParser.prototype.loadBuffer = function (bufferIndex) {

            var bufferDef = this.json.buffers[bufferIndex];
            var loader = this.fileLoader;

            if (bufferDef.type && bufferDef.type !== 'arraybuffer') {

                throw new Error('THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.');

            }

            // If present, GLB container is required to be the first buffer.
            if (bufferDef.uri === undefined && bufferIndex === 0) {

                return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body);

            }

            var options = this.options;

            return new Promise(function (resolve, reject) {

                loader.load(resolveURL(bufferDef.uri, options.path), resolve, undefined, function () {

                    reject(new Error('THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'));

                });

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
         * @param {number} bufferViewIndex
         * @return {Promise<ArrayBuffer>}
         */
        GLTFParser.prototype.loadBufferView = function (bufferViewIndex) {

            var bufferViewDef = this.json.bufferViews[bufferViewIndex];

            return this.getDependency('buffer', bufferViewDef.buffer).then(function (buffer) {

                var byteLength = bufferViewDef.byteLength || 0;
                var byteOffset = bufferViewDef.byteOffset || 0;
                return buffer.slice(byteOffset, byteOffset + byteLength);

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
         * @param {number} accessorIndex
         * @return {Promise<THREE.BufferAttribute|THREE.InterleavedBufferAttribute>}
         */
        GLTFParser.prototype.loadAccessor = function (accessorIndex) {

            var parser = this;
            var json = this.json;

            var accessorDef = this.json.accessors[accessorIndex];

            if (accessorDef.bufferView === undefined && accessorDef.sparse === undefined) {

                // Ignore empty accessors, which may be used to declare runtime
                // information about attributes coming from another source (e.g. Draco
                // compression extension).
                return Promise.resolve(null);

            }

            var pendingBufferViews = [];

            if (accessorDef.bufferView !== undefined) {

                pendingBufferViews.push(this.getDependency('bufferView', accessorDef.bufferView));

            } else {

                pendingBufferViews.push(null);

            }

            if (accessorDef.sparse !== undefined) {

                pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.indices.bufferView));
                pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.values.bufferView));

            }

            return Promise.all(pendingBufferViews).then(function (bufferViews) {

                var bufferView = bufferViews[0];

                var itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
                var TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

                // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
                var elementBytes = TypedArray.BYTES_PER_ELEMENT;
                var itemBytes = elementBytes * itemSize;
                var byteOffset = accessorDef.byteOffset || 0;
                var byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[accessorDef.bufferView].byteStride : undefined;
                var normalized = accessorDef.normalized === true;
                var array, bufferAttribute;

                // The buffer is not interleaved if the stride is the item size in bytes.
                if (byteStride && byteStride !== itemBytes) {

                    // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
                    // This makes sure that IBA.count reflects accessor.count properly
                    var ibSlice = Math.floor(byteOffset / byteStride);
                    var ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
                    var ib = parser.cache.get(ibCacheKey);

                    if (!ib) {

                        array = new TypedArray(bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes);

                        // Integer parameters to IB/IBA are in array elements, not bytes.
                        ib = new THREE.InterleavedBuffer(array, byteStride / elementBytes);

                        parser.cache.add(ibCacheKey, ib);

                    }

                    bufferAttribute = new THREE.InterleavedBufferAttribute(ib, itemSize, (byteOffset % byteStride) / elementBytes, normalized);

                } else {

                    if (bufferView === null) {

                        array = new TypedArray(accessorDef.count * itemSize);

                    } else {

                        array = new TypedArray(bufferView, byteOffset, accessorDef.count * itemSize);

                    }

                    bufferAttribute = new THREE.BufferAttribute(array, itemSize, normalized);

                }

                // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
                if (accessorDef.sparse !== undefined) {

                    var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
                    var TypedArrayIndices = WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType];

                    var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
                    var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

                    var sparseIndices = new TypedArrayIndices(bufferViews[1], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices);
                    var sparseValues = new TypedArray(bufferViews[2], byteOffsetValues, accessorDef.sparse.count * itemSize);

                    if (bufferView !== null) {

                        // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
                        bufferAttribute.setArray(bufferAttribute.array.slice());

                    }

                    for (var i = 0, il = sparseIndices.length; i < il; i++) {

                        var index = sparseIndices[i];

                        bufferAttribute.setX(index, sparseValues[i * itemSize]);
                        if (itemSize >= 2) bufferAttribute.setY(index, sparseValues[i * itemSize + 1]);
                        if (itemSize >= 3) bufferAttribute.setZ(index, sparseValues[i * itemSize + 2]);
                        if (itemSize >= 4) bufferAttribute.setW(index, sparseValues[i * itemSize + 3]);
                        if (itemSize >= 5) throw new Error('THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.');

                    }

                }

                return bufferAttribute;

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
         * @param {number} textureIndex
         * @return {Promise<THREE.Texture>}
         */
        GLTFParser.prototype.loadTexture = function (textureIndex) {

            var parser = this;
            var json = this.json;
            var options = this.options;
            var textureLoader = this.textureLoader;

            var URL = window.URL || window.webkitURL;

            var textureDef = json.textures[textureIndex];

            var textureExtensions = textureDef.extensions || {};

            var source;

            if (textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]) {

                source = json.images[textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS].source];

            } else {

                source = json.images[textureDef.source];

            }

            var sourceURI = source.uri;
            var isObjectURL = false;

            if (source.bufferView !== undefined) {

                // Load binary image data from bufferView, if provided.

                sourceURI = parser.getDependency('bufferView', source.bufferView).then(function (bufferView) {

                    isObjectURL = true;
                    var blob = new Blob([bufferView], { type: source.mimeType });
                    sourceURI = URL.createObjectURL(blob);
                    return sourceURI;

                });

            }

            return Promise.resolve(sourceURI).then(function (sourceURI) {

                // Load Texture resource.

                var loader = THREE.Loader.Handlers.get(sourceURI);

                if (!loader) {

                    loader = textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]
                        ? parser.extensions[EXTENSIONS.MSFT_TEXTURE_DDS].ddsLoader
                        : textureLoader;

                }

                return new Promise(function (resolve, reject) {

                    loader.load(resolveURL(sourceURI, options.path), resolve, undefined, reject);

                });

            }).then(function (texture) {

                // Clean up resources and configure Texture.

                if (isObjectURL === true) {

                    URL.revokeObjectURL(sourceURI);

                }

                texture.flipY = false;

                if (textureDef.name !== undefined) texture.name = textureDef.name;

                // Ignore unknown mime types, like DDS files.
                if (source.mimeType in MIME_TYPE_FORMATS) {

                    texture.format = MIME_TYPE_FORMATS[source.mimeType];

                }

                var samplers = json.samplers || {};
                var sampler = samplers[textureDef.sampler] || {};

                texture.magFilter = WEBGL_FILTERS[sampler.magFilter] || THREE.LinearFilter;
                texture.minFilter = WEBGL_FILTERS[sampler.minFilter] || THREE.LinearMipmapLinearFilter;
                texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || THREE.RepeatWrapping;
                texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || THREE.RepeatWrapping;

                return texture;

            });

        };

        /**
         * Asynchronously assigns a texture to the given material parameters.
         * @param {Object} materialParams
         * @param {string} mapName
         * @param {Object} mapDef
         * @return {Promise}
         */
        GLTFParser.prototype.assignTexture = function (materialParams, mapName, mapDef) {

            var parser = this;

            return this.getDependency('texture', mapDef.index).then(function (texture) {

                if (!texture.isCompressedTexture) {

                    switch (mapName) {

                        case 'aoMap':
                        case 'emissiveMap':
                        case 'metalnessMap':
                        case 'normalMap':
                        case 'roughnessMap':
                            texture.format = THREE.RGBFormat;
                            break;

                    }

                }

                if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {

                    var transform = mapDef.extensions !== undefined ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] : undefined;

                    if (transform) {

                        texture = parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM].extendTexture(texture, transform);

                    }

                }

                materialParams[mapName] = texture;

            });

        };

        /**
         * Assigns final material to a Mesh, Line, or Points instance. The instance
         * already has a material (generated from the glTF material options alone)
         * but reuse of the same glTF material may require multiple threejs materials
         * to accomodate different primitive types, defines, etc. New materials will
         * be created if necessary, and reused from a cache.
         * @param  {THREE.Object3D} mesh Mesh, Line, or Points instance.
         */
        GLTFParser.prototype.assignFinalMaterial = function (mesh) {

            var geometry = mesh.geometry;
            var material = mesh.material;
            var extensions = this.extensions;

            var useVertexTangents = geometry.attributes.tangent !== undefined;
            var useVertexColors = geometry.attributes.color !== undefined;
            var useFlatShading = geometry.attributes.normal === undefined;
            var useSkinning = mesh.isSkinnedMesh === true;
            var useMorphTargets = Object.keys(geometry.morphAttributes).length > 0;
            var useMorphNormals = useMorphTargets && geometry.morphAttributes.normal !== undefined;

            if (mesh.isPoints) {

                var cacheKey = 'PointsMaterial:' + material.uuid;

                var pointsMaterial = this.cache.get(cacheKey);

                if (!pointsMaterial) {

                    pointsMaterial = new THREE.PointsMaterial();
                    THREE.Material.prototype.copy.call(pointsMaterial, material);
                    pointsMaterial.color.copy(material.color);
                    pointsMaterial.map = material.map;
                    pointsMaterial.lights = false; // PointsMaterial doesn't support lights yet
                    pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px

                    this.cache.add(cacheKey, pointsMaterial);

                }

                material = pointsMaterial;

            } else if (mesh.isLine) {

                var cacheKey = 'LineBasicMaterial:' + material.uuid;

                var lineMaterial = this.cache.get(cacheKey);

                if (!lineMaterial) {

                    lineMaterial = new THREE.LineBasicMaterial();
                    THREE.Material.prototype.copy.call(lineMaterial, material);
                    lineMaterial.color.copy(material.color);
                    lineMaterial.lights = false; // LineBasicMaterial doesn't support lights yet

                    this.cache.add(cacheKey, lineMaterial);

                }

                material = lineMaterial;

            }

            // Clone the material if it will be modified
            if (useVertexTangents || useVertexColors || useFlatShading || useSkinning || useMorphTargets) {

                var cacheKey = 'ClonedMaterial:' + material.uuid + ':';

                if (material.isGLTFSpecularGlossinessMaterial) cacheKey += 'specular-glossiness:';
                if (useSkinning) cacheKey += 'skinning:';
                if (useVertexTangents) cacheKey += 'vertex-tangents:';
                if (useVertexColors) cacheKey += 'vertex-colors:';
                if (useFlatShading) cacheKey += 'flat-shading:';
                if (useMorphTargets) cacheKey += 'morph-targets:';
                if (useMorphNormals) cacheKey += 'morph-normals:';

                var cachedMaterial = this.cache.get(cacheKey);

                if (!cachedMaterial) {

                    cachedMaterial = material.isGLTFSpecularGlossinessMaterial
                        ? extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].cloneMaterial(material)
                        : material.clone();

                    if (useSkinning) cachedMaterial.skinning = true;
                    if (useVertexTangents) cachedMaterial.vertexTangents = true;
                    if (useVertexColors) cachedMaterial.vertexColors = THREE.VertexColors;
                    if (useFlatShading) cachedMaterial.flatShading = true;
                    if (useMorphTargets) cachedMaterial.morphTargets = true;
                    if (useMorphNormals) cachedMaterial.morphNormals = true;

                    this.cache.add(cacheKey, cachedMaterial);

                }

                material = cachedMaterial;

            }

            // workarounds for mesh and geometry

            if (material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined) {

                console.log('THREE.GLTFLoader: Duplicating UVs to support aoMap.');
                geometry.addAttribute('uv2', new THREE.BufferAttribute(geometry.attributes.uv.array, 2));

            }

            if (material.isGLTFSpecularGlossinessMaterial) {

                // for GLTFSpecularGlossinessMaterial(ShaderMaterial) uniforms runtime update
                mesh.onBeforeRender = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].refreshUniforms;

            }

            mesh.material = material;

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
         * @param {number} materialIndex
         * @return {Promise<THREE.Material>}
         */
        GLTFParser.prototype.loadMaterial = function (materialIndex) {

            var parser = this;
            var json = this.json;
            var extensions = this.extensions;
            var materialDef = json.materials[materialIndex];

            var materialType;
            var materialParams = {};
            var materialExtensions = materialDef.extensions || {};

            var pending = [];

            if (materialExtensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]) {

                var sgExtension = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS];
                materialType = sgExtension.getMaterialType();
                pending.push(sgExtension.extendParams(materialParams, materialDef, parser));

            } else if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {

                var kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT];
                materialType = kmuExtension.getMaterialType();
                pending.push(kmuExtension.extendParams(materialParams, materialDef, parser));

            } else {

                // Specification:
                // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

                materialType = THREE.MeshStandardMaterial;

                var metallicRoughness = materialDef.pbrMetallicRoughness || {};

                materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
                materialParams.opacity = 1.0;

                if (Array.isArray(metallicRoughness.baseColorFactor)) {

                    var array = metallicRoughness.baseColorFactor;

                    materialParams.color.fromArray(array);
                    materialParams.opacity = array[3];

                }

                if (metallicRoughness.baseColorTexture !== undefined) {

                    pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));

                }

                materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
                materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;

                if (metallicRoughness.metallicRoughnessTexture !== undefined) {

                    pending.push(parser.assignTexture(materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture));
                    pending.push(parser.assignTexture(materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture));

                }

            }

            if (materialDef.doubleSided === true) {

                materialParams.side = THREE.DoubleSide;

            }

            var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

            if (alphaMode === ALPHA_MODES.BLEND) {

                materialParams.transparent = true;

            } else {

                materialParams.transparent = false;

                if (alphaMode === ALPHA_MODES.MASK) {

                    materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;

                }

            }

            if (materialDef.normalTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

                pending.push(parser.assignTexture(materialParams, 'normalMap', materialDef.normalTexture));

                materialParams.normalScale = new THREE.Vector2(1, 1);

                if (materialDef.normalTexture.scale !== undefined) {

                    materialParams.normalScale.set(materialDef.normalTexture.scale, materialDef.normalTexture.scale);

                }

            }

            if (materialDef.occlusionTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

                pending.push(parser.assignTexture(materialParams, 'aoMap', materialDef.occlusionTexture));

                if (materialDef.occlusionTexture.strength !== undefined) {

                    materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;

                }

            }

            if (materialDef.emissiveFactor !== undefined && materialType !== THREE.MeshBasicMaterial) {

                materialParams.emissive = new THREE.Color().fromArray(materialDef.emissiveFactor);

            }

            if (materialDef.emissiveTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

                pending.push(parser.assignTexture(materialParams, 'emissiveMap', materialDef.emissiveTexture));

            }

            return Promise.all(pending).then(function () {

                var material;

                if (materialType === THREE.ShaderMaterial) {

                    material = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].createMaterial(materialParams);

                } else {

                    material = new materialType(materialParams);

                }

                if (materialDef.name !== undefined) material.name = materialDef.name;

                // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
                if (material.map) material.map.encoding = THREE.sRGBEncoding;
                if (material.emissiveMap) material.emissiveMap.encoding = THREE.sRGBEncoding;
                if (material.specularMap) material.specularMap.encoding = THREE.sRGBEncoding;

                assignExtrasToUserData(material, materialDef);

                if (materialDef.extensions) addUnknownExtensionsToUserData(extensions, material, materialDef);

                return material;

            });

        };

        /**
         * @param {THREE.BufferGeometry} geometry
         * @param {GLTF.Primitive} primitiveDef
         * @param {GLTFParser} parser
         * @return {Promise<THREE.BufferGeometry>}
         */
        function addPrimitiveAttributes(geometry, primitiveDef, parser) {

            var attributes = primitiveDef.attributes;

            var pending = [];

            function assignAttributeAccessor(accessorIndex, attributeName) {

                return parser.getDependency('accessor', accessorIndex)
                    .then(function (accessor) {

                        geometry.addAttribute(attributeName, accessor);

                    });

            }

            for (var gltfAttributeName in attributes) {

                var threeAttributeName = ATTRIBUTES[gltfAttributeName] || gltfAttributeName.toLowerCase();

                // Skip attributes already provided by e.g. Draco extension.
                if (threeAttributeName in geometry.attributes) continue;

                pending.push(assignAttributeAccessor(attributes[gltfAttributeName], threeAttributeName));

            }

            if (primitiveDef.indices !== undefined && !geometry.index) {

                var accessor = parser.getDependency('accessor', primitiveDef.indices).then(function (accessor) {

                    geometry.setIndex(accessor);

                });

                pending.push(accessor);

            }

            assignExtrasToUserData(geometry, primitiveDef);

            return Promise.all(pending).then(function () {

                return primitiveDef.targets !== undefined
                    ? addMorphTargets(geometry, primitiveDef.targets, parser)
                    : geometry;

            });

        }

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
         *
         * Creates BufferGeometries from primitives.
         *
         * @param {Array<GLTF.Primitive>} primitives
         * @return {Promise<Array<THREE.BufferGeometry>>}
         */
        GLTFParser.prototype.loadGeometries = function (primitives) {

            var parser = this;
            var extensions = this.extensions;
            var cache = this.primitiveCache;

            function createDracoPrimitive(primitive) {

                return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
                    .decodePrimitive(primitive, parser)
                    .then(function (geometry) {

                        return addPrimitiveAttributes(geometry, primitive, parser);

                    });

            }

            var pending = [];

            for (var i = 0, il = primitives.length; i < il; i++) {

                var primitive = primitives[i];
                var cacheKey = createPrimitiveKey(primitive);

                // See if we've already created this geometry
                var cached = cache[cacheKey];

                if (cached) {

                    // Use the cached geometry if it exists
                    pending.push(cached.promise);

                } else {

                    var geometryPromise;

                    if (primitive.extensions && primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]) {

                        // Use DRACO geometry if available
                        geometryPromise = createDracoPrimitive(primitive);

                    } else {

                        // Otherwise create a new geometry
                        geometryPromise = addPrimitiveAttributes(new THREE.BufferGeometry(), primitive, parser);

                    }

                    // Cache this geometry
                    cache[cacheKey] = { primitive: primitive, promise: geometryPromise };

                    pending.push(geometryPromise);

                }

            }

            return Promise.all(pending);

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
         * @param {number} meshIndex
         * @return {Promise<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
         */
        GLTFParser.prototype.loadMesh = function (meshIndex) {

            var parser = this;
            var json = this.json;

            var meshDef = json.meshes[meshIndex];
            var primitives = meshDef.primitives;

            var pending = [];

            for (var i = 0, il = primitives.length; i < il; i++) {

                var material = primitives[i].material === undefined
                    ? createDefaultMaterial()
                    : this.getDependency('material', primitives[i].material);

                pending.push(material);

            }

            return Promise.all(pending).then(function (originalMaterials) {

                return parser.loadGeometries(primitives).then(function (geometries) {

                    var meshes = [];

                    for (var i = 0, il = geometries.length; i < il; i++) {

                        var geometry = geometries[i];
                        var primitive = primitives[i];

                        // 1. create Mesh

                        var mesh;

                        var material = originalMaterials[i];

                        if (primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
                            primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
                            primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
                            primitive.mode === undefined) {

                            // .isSkinnedMesh isn't in glTF spec. See .markDefs()
                            mesh = meshDef.isSkinnedMesh === true
                                ? new THREE.SkinnedMesh(geometry, material)
                                : new THREE.Mesh(geometry, material);

                            if (mesh.isSkinnedMesh === true && !mesh.geometry.attributes.skinWeight.normalized) {

                                // we normalize floating point skin weight array to fix malformed assets (see #15319)
                                // it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
                                mesh.normalizeSkinWeights();

                            }

                            if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {

                                mesh.drawMode = THREE.TriangleStripDrawMode;

                            } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {

                                mesh.drawMode = THREE.TriangleFanDrawMode;

                            }

                        } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {

                            mesh = new THREE.LineSegments(geometry, material);

                        } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {

                            mesh = new THREE.Line(geometry, material);

                        } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {

                            mesh = new THREE.LineLoop(geometry, material);

                        } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {

                            mesh = new THREE.Points(geometry, material);

                        } else {

                            throw new Error('THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode);

                        }

                        if (Object.keys(mesh.geometry.morphAttributes).length > 0) {

                            updateMorphTargets(mesh, meshDef);

                        }

                        mesh.name = meshDef.name || ('mesh_' + meshIndex);

                        if (geometries.length > 1) mesh.name += '_' + i;

                        assignExtrasToUserData(mesh, meshDef);

                        parser.assignFinalMaterial(mesh);

                        meshes.push(mesh);

                    }

                    if (meshes.length === 1) {

                        return meshes[0];

                    }

                    var group = new THREE.Group();

                    for (var i = 0, il = meshes.length; i < il; i++) {

                        group.add(meshes[i]);

                    }

                    return group;

                });

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
         * @param {number} cameraIndex
         * @return {Promise<THREE.Camera>}
         */
        GLTFParser.prototype.loadCamera = function (cameraIndex) {

            var camera;
            var cameraDef = this.json.cameras[cameraIndex];
            var params = cameraDef[cameraDef.type];

            if (!params) {

                console.warn('THREE.GLTFLoader: Missing camera parameters.');
                return;

            }

            if (cameraDef.type === 'perspective') {

                camera = new THREE.PerspectiveCamera(THREE.Math.radToDeg(params.yfov), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6);

            } else if (cameraDef.type === 'orthographic') {

                camera = new THREE.OrthographicCamera(params.xmag / - 2, params.xmag / 2, params.ymag / 2, params.ymag / - 2, params.znear, params.zfar);

            }

            if (cameraDef.name !== undefined) camera.name = cameraDef.name;

            assignExtrasToUserData(camera, cameraDef);

            return Promise.resolve(camera);

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
         * @param {number} skinIndex
         * @return {Promise<Object>}
         */
        GLTFParser.prototype.loadSkin = function (skinIndex) {

            var skinDef = this.json.skins[skinIndex];

            var skinEntry = { joints: skinDef.joints };

            if (skinDef.inverseBindMatrices === undefined) {

                return Promise.resolve(skinEntry);

            }

            return this.getDependency('accessor', skinDef.inverseBindMatrices).then(function (accessor) {

                skinEntry.inverseBindMatrices = accessor;

                return skinEntry;

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
         * @param {number} animationIndex
         * @return {Promise<THREE.AnimationClip>}
         */
        GLTFParser.prototype.loadAnimation = function (animationIndex) {

            var json = this.json;

            var animationDef = json.animations[animationIndex];

            var pendingNodes = [];
            var pendingInputAccessors = [];
            var pendingOutputAccessors = [];
            var pendingSamplers = [];
            var pendingTargets = [];

            for (var i = 0, il = animationDef.channels.length; i < il; i++) {

                var channel = animationDef.channels[i];
                var sampler = animationDef.samplers[channel.sampler];
                var target = channel.target;
                var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
                var input = animationDef.parameters !== undefined ? animationDef.parameters[sampler.input] : sampler.input;
                var output = animationDef.parameters !== undefined ? animationDef.parameters[sampler.output] : sampler.output;

                pendingNodes.push(this.getDependency('node', name));
                pendingInputAccessors.push(this.getDependency('accessor', input));
                pendingOutputAccessors.push(this.getDependency('accessor', output));
                pendingSamplers.push(sampler);
                pendingTargets.push(target);

            }

            return Promise.all([

                Promise.all(pendingNodes),
                Promise.all(pendingInputAccessors),
                Promise.all(pendingOutputAccessors),
                Promise.all(pendingSamplers),
                Promise.all(pendingTargets)

            ]).then(function (dependencies) {

                var nodes = dependencies[0];
                var inputAccessors = dependencies[1];
                var outputAccessors = dependencies[2];
                var samplers = dependencies[3];
                var targets = dependencies[4];

                var tracks = [];

                for (var i = 0, il = nodes.length; i < il; i++) {

                    var node = nodes[i];
                    var inputAccessor = inputAccessors[i];
                    var outputAccessor = outputAccessors[i];
                    var sampler = samplers[i];
                    var target = targets[i];

                    if (node === undefined) continue;

                    node.updateMatrix();
                    node.matrixAutoUpdate = true;

                    var TypedKeyframeTrack;

                    switch (PATH_PROPERTIES[target.path]) {

                        case PATH_PROPERTIES.weights:

                            TypedKeyframeTrack = THREE.NumberKeyframeTrack;
                            break;

                        case PATH_PROPERTIES.rotation:

                            TypedKeyframeTrack = THREE.QuaternionKeyframeTrack;
                            break;

                        case PATH_PROPERTIES.position:
                        case PATH_PROPERTIES.scale:
                        default:

                            TypedKeyframeTrack = THREE.VectorKeyframeTrack;
                            break;

                    }

                    var targetName = node.name ? node.name : node.uuid;

                    var interpolation = sampler.interpolation !== undefined ? INTERPOLATION[sampler.interpolation] : THREE.InterpolateLinear;

                    var targetNames = [];

                    if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {

                        // Node may be a THREE.Group (glTF mesh with several primitives) or a THREE.Mesh.
                        node.traverse(function (object) {

                            if (object.isMesh === true && object.morphTargetInfluences) {

                                targetNames.push(object.name ? object.name : object.uuid);

                            }

                        });

                    } else {

                        targetNames.push(targetName);

                    }

                    var outputArray = outputAccessor.array;

                    if (outputAccessor.normalized) {

                        var scale;

                        if (outputArray.constructor === Int8Array) {

                            scale = 1 / 127;

                        } else if (outputArray.constructor === Uint8Array) {

                            scale = 1 / 255;

                        } else if (outputArray.constructor == Int16Array) {

                            scale = 1 / 32767;

                        } else if (outputArray.constructor === Uint16Array) {

                            scale = 1 / 65535;

                        } else {

                            throw new Error('THREE.GLTFLoader: Unsupported output accessor component type.');

                        }

                        var scaled = new Float32Array(outputArray.length);

                        for (var j = 0, jl = outputArray.length; j < jl; j++) {

                            scaled[j] = outputArray[j] * scale;

                        }

                        outputArray = scaled;

                    }

                    for (var j = 0, jl = targetNames.length; j < jl; j++) {

                        var track = new TypedKeyframeTrack(
                            targetNames[j] + '.' + PATH_PROPERTIES[target.path],
                            inputAccessor.array,
                            outputArray,
                            interpolation
                        );

                        // Override interpolation with custom factory method.
                        if (sampler.interpolation === 'CUBICSPLINE') {

                            track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline(result) {

                                // A CUBICSPLINE keyframe in glTF has three output values for each input value,
                                // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
                                // must be divided by three to get the interpolant's sampleSize argument.

                                return new GLTFCubicSplineInterpolant(this.times, this.values, this.getValueSize() / 3, result);

                            };

                            // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
                            track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;

                        }

                        tracks.push(track);

                    }

                }

                var name = animationDef.name !== undefined ? animationDef.name : 'animation_' + animationIndex;

                return new THREE.AnimationClip(name, undefined, tracks);

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
         * @param {number} nodeIndex
         * @return {Promise<THREE.Object3D>}
         */
        GLTFParser.prototype.loadNode = function (nodeIndex) {

            var json = this.json;
            var extensions = this.extensions;
            var parser = this;

            var meshReferences = json.meshReferences;
            var meshUses = json.meshUses;

            var nodeDef = json.nodes[nodeIndex];

            return (function () {

                var pending = [];

                if (nodeDef.mesh !== undefined) {

                    pending.push(parser.getDependency('mesh', nodeDef.mesh).then(function (mesh) {

                        var node;

                        if (meshReferences[nodeDef.mesh] > 1) {

                            var instanceNum = meshUses[nodeDef.mesh]++;

                            node = mesh.clone();
                            node.name += '_instance_' + instanceNum;

                            // onBeforeRender copy for Specular-Glossiness
                            node.onBeforeRender = mesh.onBeforeRender;

                            for (var i = 0, il = node.children.length; i < il; i++) {

                                node.children[i].name += '_instance_' + instanceNum;
                                node.children[i].onBeforeRender = mesh.children[i].onBeforeRender;

                            }

                        } else {

                            node = mesh;

                        }

                        // if weights are provided on the node, override weights on the mesh.
                        if (nodeDef.weights !== undefined) {

                            node.traverse(function (o) {

                                if (!o.isMesh) return;

                                for (var i = 0, il = nodeDef.weights.length; i < il; i++) {

                                    o.morphTargetInfluences[i] = nodeDef.weights[i];

                                }

                            });

                        }

                        return node;

                    }));

                }

                if (nodeDef.camera !== undefined) {

                    pending.push(parser.getDependency('camera', nodeDef.camera));

                }

                if (nodeDef.extensions
                    && nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]
                    && nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light !== undefined) {

                    pending.push(parser.getDependency('light', nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light));

                }

                return Promise.all(pending);

            }()).then(function (objects) {

                var node;

                // .isBone isn't in glTF spec. See .markDefs
                if (nodeDef.isBone === true) {

                    node = new THREE.Bone();

                } else if (objects.length > 1) {

                    node = new THREE.Group();

                } else if (objects.length === 1) {

                    node = objects[0];

                } else {

                    node = new THREE.Object3D();

                }

                if (node !== objects[0]) {

                    for (var i = 0, il = objects.length; i < il; i++) {

                        node.add(objects[i]);

                    }

                }

                if (nodeDef.name !== undefined) {

                    node.userData.name = nodeDef.name;
                    node.name = THREE.PropertyBinding.sanitizeNodeName(nodeDef.name);

                }

                assignExtrasToUserData(node, nodeDef);

                if (nodeDef.extensions) addUnknownExtensionsToUserData(extensions, node, nodeDef);

                if (nodeDef.matrix !== undefined) {

                    var matrix = new THREE.Matrix4();
                    matrix.fromArray(nodeDef.matrix);
                    node.applyMatrix(matrix);

                } else {

                    if (nodeDef.translation !== undefined) {

                        node.position.fromArray(nodeDef.translation);

                    }

                    if (nodeDef.rotation !== undefined) {

                        node.quaternion.fromArray(nodeDef.rotation);

                    }

                    if (nodeDef.scale !== undefined) {

                        node.scale.fromArray(nodeDef.scale);

                    }

                }

                return node;

            });

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
         * @param {number} sceneIndex
         * @return {Promise<THREE.Scene>}
         */
        GLTFParser.prototype.loadScene = function () {

            // scene node hierachy builder

            function buildNodeHierachy(nodeId, parentObject, json, parser) {

                var nodeDef = json.nodes[nodeId];

                return parser.getDependency('node', nodeId).then(function (node) {

                    if (nodeDef.skin === undefined) return node;

                    // build skeleton here as well

                    var skinEntry;

                    return parser.getDependency('skin', nodeDef.skin).then(function (skin) {

                        skinEntry = skin;

                        var pendingJoints = [];

                        for (var i = 0, il = skinEntry.joints.length; i < il; i++) {

                            pendingJoints.push(parser.getDependency('node', skinEntry.joints[i]));

                        }

                        return Promise.all(pendingJoints);

                    }).then(function (jointNodes) {

                        node.traverse(function (mesh) {

                            if (!mesh.isMesh) return;

                            var bones = [];
                            var boneInverses = [];

                            for (var j = 0, jl = jointNodes.length; j < jl; j++) {

                                var jointNode = jointNodes[j];

                                if (jointNode) {

                                    bones.push(jointNode);

                                    var mat = new THREE.Matrix4();

                                    if (skinEntry.inverseBindMatrices !== undefined) {

                                        mat.fromArray(skinEntry.inverseBindMatrices.array, j * 16);

                                    }

                                    boneInverses.push(mat);

                                } else {

                                    console.warn('THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[j]);

                                }

                            }

                            mesh.bind(new THREE.Skeleton(bones, boneInverses), mesh.matrixWorld);

                        });

                        return node;

                    });

                }).then(function (node) {

                    // build node hierachy

                    parentObject.add(node);

                    var pending = [];

                    if (nodeDef.children) {

                        var children = nodeDef.children;

                        for (var i = 0, il = children.length; i < il; i++) {

                            var child = children[i];
                            pending.push(buildNodeHierachy(child, node, json, parser));

                        }

                    }

                    return Promise.all(pending);

                });

            }

            return function loadScene(sceneIndex) {

                var json = this.json;
                var extensions = this.extensions;
                var sceneDef = this.json.scenes[sceneIndex];
                var parser = this;

                var scene = new THREE.Scene();
                if (sceneDef.name !== undefined) scene.name = sceneDef.name;

                assignExtrasToUserData(scene, sceneDef);

                if (sceneDef.extensions) addUnknownExtensionsToUserData(extensions, scene, sceneDef);

                var nodeIds = sceneDef.nodes || [];

                var pending = [];

                for (var i = 0, il = nodeIds.length; i < il; i++) {

                    pending.push(buildNodeHierachy(nodeIds[i], scene, json, parser));

                }

                return Promise.all(pending).then(function () {

                    return scene;

                });

            };

        }();

        return GLTFLoader;

    })();
}